This post describes the ISIS Segment Routing IPv6 (SRv6) with FRR (FRRouting) and Ubuntu (WSL).
Code repositories
Credits:
Code authours: Carmine Scarpitta and Dmytro Shytyi.
[PART1] SRv6 multiple segs SIDs series of patches
[PART2] ISIS SRv6 series of patches
I would like to thank for a review: @cscarpitta @pushpasis @donaldsharp @routingrocks and @riw777.
Linux support
Ubuntu 22.04 within WSL was used for the testbed with kernel that has activated LW_TUNNELs (CONFIG_IPV6_SEG6_LWTUNNEL)
0root@munet:/# uname -a
1Linux munet 5.15.90.4-microsoft-standard-WSL2+ #1 SMP Fri Jul 28 00:56:47 CEST 2023 x86_64 x86_64 x86_64 GNU/Linux
Consider to activate Sysfs variable such as “Seg6 seg6_enabled” and/or “sysctl -w net.ipv6.conf.all.forwarding=1”.
FRR configuration
r1:
ipv6 route 2001:db8::/64 r1-r4 segs fc00:0:6::/fc00:0:5::/fc00:0:4::
!
interface lo
ip address 1.1.1.1/32
ip router isis 1
ipv6 address fc00:0:1::1/128
ipv6 router isis 1
isis passive
exit
!
interface r1-r2
ip address 10.0.1.1/24
ip router isis 1
ipv6 router isis 1
isis hello-multiplier 3
exit
!
interface r1-r4
ip address 10.0.4.1/24
ip router isis 1
ipv6 router isis 1
isis hello-multiplier 3
exit
!
router isis 1
is-type level-1
net 49.0000.0000.0000.0001.00
lsp-timers gen-interval 2 refresh-interval 900 max-lifetime 1200
topology ipv6-unicast
segment-routing srv6
locator loc1
exit
!
segment-routing
srv6
locators
locator loc1
prefix fc00:0:1::/48 block-len 32 node-len 16 func-bits 16
exit
!
exit
!
exit
!
exit
!
endr2:
interface lo
ip address 2.2.2.2/32
ip router isis 1
ipv6 address fc00:0:2::1/128
ipv6 router isis 1
isis passive
exit
!
interface r2-r1
ip address 10.0.1.2/24
ip router isis 1
ipv6 router isis 1
isis hello-multiplier 3 exit ! interface r2-r3 ip address 10.0.2.2/24 ip router isis 1 ipv6 router isis 1 isis hello-multiplier 3 exit ! router isis 1 is-type level-1 net 49.0000.0000.0000.0002.00 lsp-timers gen-interval 2 refresh-interval 900 max-lifetime 1200 topology ipv6-unicast segment-routing srv6 locator loc1 exit ! segment-routing srv6 locators locator loc1 prefix fc00:0:2::/48 block-len 32 node-len 16 func-bits 16 exit ! exit ! exit ! exit ! end
r7:
!
interface lo
ip address 7.7.7.7/32
ip router isis 1
ipv6 address fc00:0:7::1/128
ipv6 router isis 1
isis passive
exit
!
interface r7-r3
ip address 10.0.3.7/24
ip router isis 1
ipv6 router isis 1
isis hello-multiplier 3
exit
!
interface r7-r6
ip address 10.0.7.7/24
ip router isis 1
ipv6 router isis 1
isis hello-multiplier 3
exit
!
router isis 1
is-type level-1
net 49.0000.0000.0000.0007.00
lsp-timers gen-interval 2 refresh-interval 900 max-lifetime 1200
topology ipv6-unicast
segment-routing srv6
locator loc1
exit
!
segment-routing
srv6
locators
locator loc1
prefix fc00:0:7::/48 block-len 32 node-len 16 func-bits 16
exit
!
exit
!
exit
!
exit
!
end
Display SRv6 route on r1
FRR:
r1# show ipv6 route
Codes: K - kernel route, C - connected, S - static, R - RIPng,
O - OSPFv3, I - IS-IS, B - BGP, T - Table, v - VNC,
V - VNC-Direct, A - Babel, F - PBR, f - OpenFabric,
> - selected route, * - FIB route, q - queued, r - rejected, b - backup
t - trapped, o - offload failure
S>* 2001:db8::/64 [1/0] is directly connected, r1-r4, seg6 fc00:0:6::,fc00:0:5::,fc00:0:4::, weight 1, 01:52:08
[..]iproute2:
root@r1:/# ip -6 route
2001:db8::/64 nhid 41 encap seg6 mode encap segs 3 [ fc00:0:4:: fc00:0:5:: fc00:0:6:: ] dev r1-r4 proto 196 metric 20 pref mediumDisplay ISIS SRv6 seg6local behavior on R2
The same seg6local behavior is bootstrapped on r3, r4, r5, r6, r7 nodes.
r2 router:
r2# show ipv6 route
Codes: K - kernel route, C - connected, S - static, R - RIPng,
O - OSPFv3, I - IS-IS, B - BGP, T - Table, v - VNC,
V - VNC-Direct, A - Babel, F - PBR, f - OpenFabric,
> - selected route, * - FIB route, q - queued, r - rejected, b - backup
t - trapped, o - offload failure
[..]
I>* fc00:0:2::/128 [115/0] is directly connected, sr0, seg6local End USP, weight 1, 02:34:25r5 router:
r5# show ipv6 route
Codes: K - kernel route, C - connected, S - static, R - RIPng,
O - OSPFv3, I - IS-IS, B - BGP, T - Table, v - VNC,
V - VNC-Direct, A - Babel, F - PBR, f - OpenFabric,
> - selected route, * - FIB route, q - queued, r - rejected, b - backup
t - trapped, o - offload failure
[..]
I>* fc00:0:5::/128 [115/0] is directly connected, sr0, seg6local End USP, weight 1, 02:37:17
Testbed consoles presented with routers indexes
This figure is related to the network topology presented in the top of article. This figure describes router placement that doesn’t change in future figures.
Testbed – echo request/reply based on ISIS SPF (RED Line in the first figure)
This figure is related to the network topology presented in the top of article. This figure describes the echo “request”/”reply” process in regular setup. Echo request is sent via SPF (r1-r2-r3-r7) – red line in the first figure. Echo reply is returned in vise-versa manner.
Testbed – echo request/reply based with SRv6 features (Blue SRv6 Low-Latency tunnel)
This figure is related to the network topology presented in the top of article. This figure describes the echo “request”/”reply” process witch SRv6 features.
Echo request is sent via the low-latency path (r1-r4-r5-r6-r7) using the SRv6 route and returned by regular path (r7-r3-r2-r1).
Thank your for reading!